First Wind Event of the Winter Season

It blustery out there this morning as a Pacific cyclone passed to our north.  As shown by the maximum gust map, winds gusted to 30-40 mph in exposed areas around Puget Sound and 40-55 mph in the mountains.

The cause?   A low center that moved into central British Columbia (see pressure analysis at  5AM this morning,  below).  The low center was not something you would write home about (991 hPa), but there was a strong pressure gradient south of the low that caused winds to accelerate from the south.

A higher resolution map at 8 AM shows the large pressure gradient more clearly.  The lines are isobars, lines of constant pressure, and the pressure gradient is greatest when the lines are closer together.  Large pressure gradient or change means strong winds.

The infrared satellite image at 5 AM this morning shows the tight low pressure making landfall on the BC coast (look for tightly curved clouds associated with the low center)

The visible satellite image at 1 PM today was beautiful....and very typical of winter.  A well formed cyclone and attendant fronts was east of the west coast and south of the Aleutians.    You see the "popcorn-like" clouds swirling into it?  That indicates great vertical instability with cold air over much warmer water.  A frontal band was sweeping into the Pacific Northwest, and a little "comma cloud", associate with an upper-level trough was due west of Vancouver Is.   A great image to use in class.

 Tomorrow (Saturday) show be dry in the morning and early/mid afternoon for Puget Sound, but substantial rain will move in during the evening.  Heavy rain overnight and more showers on Sunday.   As I warned in a previous blog, we have made the winter transition, and you won't see too many dry days in a row for a while.





from Cliff Mass Weather and Climate Blog https://ift.tt/2O5qmOc